Process for recovering oil utilizing non-newtonian fluids



PIP H12 OR 392799537 Oc 1 1966 w. B. KIRK, JR ETAL PROCESS FOR RECOVERING OIL UTILIZING NON-NEWTONIAN FLUIDS Filed Jan. 10, 1964 IOOO- guhhnu INVENTORS WALTER B. KIRK, JR. I WILSON L. KINNEY WILLIAM B. GOGA RTY BY A TTORNE4 United States Patent 3,279,537 PRQCESS FOR RECOVERING OIL UTILIZING NON-NEWTONIAN FLUIDS Walter B. Kirk, .Ir., and Wilson L. Kinney, Terre Haute, Ind., and William B. Gogarty, Littleton, Colo., assignors to Marathon Oil Company, Findlay, Ohio, 21 corporation of Ohio Filed Jan. 10, 1964, Ser. No. 337,015 15 Claims. (Cl. 1669) This invention relates to the injection and flow of pseudoplastic non-Newtonian fluids in oil-bearing formations, and more particularly to a process for intermittent reduction and subsequent increase in pumping pressures in the injection and driving of non-Newtonian fluids into and through subterranean oil-bearing formations.

One bank method of flooding uses a slug of thickened material followed by a slug of a driving material such as water. The thickening materials are usually long chain polymers such as carboxylmethyl cellulose or po-lyacrylic acid in water solution. These materials give the solutions pseudoplastic non-Newtonian viscosity characteristics.

Non-Newtonian fluids are complex solutions that sometimes exhibit colloidal tendencies. Non-Newtonian solutions or mixtures do not show a linear relationship between shear rate and shear stress, i.e., the apparent viscosity of the liquid decreases wth increasing shear stress. Aqueous solutions of copolymers of vinyl compounds with ethylene, styrene, maleic anhydride (United States Patent 3,070,158) and polyvinyl toluene sulfonates, polystyrene sulfonates, or substituted polystyrene sulfonates (United States Patent 3,085,063) are other examples of materials which exhibit pseudoplastic non-Newtonian,

characteristics in reservoirs.

The injection rate of most fluids utilized in petroleum recovery from subterranean formations to date has been relatively uniform. One exception has been the use of high cyclic injection rates to increase production by use of the principle of imbibition in a fractured oil bearing formation (A.I.M.E., S.P.E. Journal of Petroleum Technology, vol. XV, No. 8, pp. 87784, August 1963). This process is in no Way related to our method of flooding because the principle used in our method is that of increased pressure differential across a non-Newtonian fluid.

We have now discovered that when at least one slug of a material exhibiting non-Newtonian flow properties in a reservoir is injected into a formation and thereafter injection .pressures are intermittently reduced and subsequently instantaneously increased, the flow of the non- Newtonian fluid through the reservoir causes a great increase in fluid productivity at a production well. Our preferred method uses a bank having at least one slug of a material exhibiting pseudoplastic non-Newtonian flow properties in the reservoir with substantially coincident drawdown of recovery wells. A portion of the injected fluids, preferably the drive fluid, can be Newtonian in character.

The apparent viscosity of a pseudoplastic non-Newtonian fluid flowing in a porous medium increases as flow decreases. Apparent viscosity, stated another way, is the ratio of shear stress to rate of shear, the shear stress exhibited by the fluid being the result of the particular rate of shear.

The following figures and theoretical explanations aid in understanding this invention and the phenomenon underlying the invention.

FIGURE 1 depicts the relationship between apparent viscosity, ,u and the rate of flow, q in a pseudoplastic non-Newtonian fluid.

FIGURE 2 shows an experimentally derive-d relationship between the logarithm of the difference in pressure 3,279,537 Patented Oct. 18, 1966 across a linear porous medium divided by the rate of flow, AP/ q, and the rate of flow, q.

FIGURE 3 depicts typical pressure curves between an injection well at 0 feet and a production well at about 233 feet where the slug of non-Newtonian fluid is situated between and feet from the injection well.

A graph of the log of pressure difference in a porous medium divded by the rate of fluid flow versus the log of the rate of fluid flow, represented by FIG. 2, shows Newtonian fluid flow as a straight horizontal line 11 and non-Newtonian fluid flow as a straight inclined line 12 where the distance through the porous medium, permeability, cross-sectional area of the porous medium, etc., are constant. Horizontal line 11 is the expected result of Darcys law. Solution of the equation of inclined line 12, as follows, gives us the following equation:

where q=rate of flow, C=constant, AP=pressure difference, and n=the exponent arising out of the character of the injected fluid. In Newtonian fluids n=l, while in non-Newtonian fluids n= l.

From graph 2, it is evident that in formulating an equation for the sloped line that where AP=pressure difference across core, q=flow, N=slope of line, i.e., R/r (denoted at FIG. 2), and C=constant.

By using the laws of logarithms, we can say This expression can be converted to where C is a diflFerent constant than C and From this relationship, it is evident that an increase in AP will increase the volumetric flow rate, q, exponentially. Therefore, at equal initial apparent viscosities and injection pressures, proportionately larger changes in flow rate can be obtained for non-Newtonian fluids.

The improved results obtained by the process of this invention are explainable in terms of the idealized curves of FIG. 3. The curves are drawn in terms of the distance between an injection well and a production well on a 2.5 acre regular isolated five-spot pattern wherein fluid is injected into the four areally external wells of the five-spot pattern and oil is continuously pumped from the central well.

In considering the curves, it must be remembered that the apparent viscosity will increase rapidly with decreasing rate of movement of the pseudoplastic non-Newtonian fluid through the formation. Thus, if fluid injection is stopped, the apparent viscosity of the non-Newtonian fluid in the formation will increase as the flow rate decreases.

Curves 13, 14, and 17 depict the pressure profile within a formation where a pseudoplastic non-Newtonian bank is located between lines 15 and 16. Curve 13 indicates the pressure profile across the bank at a constant, i.e., steady state, injection pressure of about 1,250 psi. Curve 14 depicts the pressure profile after injection of fluids has been discontinued two or three days previously.

3 Curve 17 depicts the pressure profile after injection of a Newtonian fluid, such as water, is resumed at 1,250 p.s.i. pressure.

It is seen that normally during steady state opera- 4. In an oil recovery process wherein a bank of fluid, including at least one slug of a non-Newtonian fluid, is propelled by fluid pressure through a subterranean oilbearing formation from at least one injection well drilled tion the pressure difference across the bank will be 1,000 5 into said formation to at least one production well drilled p.s.i. while the pressure drop across the bank, after reinto said formation, the steps comprising cyclically reinjection, is about 1,200 p.s.i. due to continued drawducing and rapidly increasing the injection fluid pressure down. This greater pressure difference causes a greater acting on the bank of fluid and producing oil from said shear and, as a result, a reduced viscosity which, in turn, at least one production well. leads to greater rate of flow. 5. The process of claim 4 comprising maintaining The initial increase in pressure across the bank causes drawdown at the production well(s) substantially coinan increase in flow at the production well which decreases cident with the reduction of injected fluid pressures. as further transients develop in the formation. How- 6. The process of claim 5 comprising reducing the ever, the flow rate will, for a period of time, remain injected fluid pressure to substantially zero. higher than the previous steady state flow rate. 7. The process comprising injecting into a subterranean The following example more illustrates our invention, permeable oil-bearing formation, through a portion of but it is not intended that the invention be limited to the a plurality of wells drilled therein, at least one fluid havconditions or materials of the example. Rather, it is ing pseudoplastic non-Newtonian viscosity characteristics; intended that all equivalents obvious to those skilled in thereafter, injecting into said formation through said the art be included in the scope of our invention as portion of wells a drive material having Newtonian visclaimed. cosity characteristics and periodically substantially re- Example I ducing, thereafter substantially instantly increasing the l rate at which the drive material is injected into said. A Slug, Comprising 3% of the P Volume of a format formation and producing oil through a second portion of tion, of a soluble oil is injected into the four injection said plurality f Wells. wells of an isolated regular five-spot pattern drilled into 3 h process f claim 7 comprising continuing a 10-f00t thick Producing Sandstone located at a depth of duction from the second portion of the Wells drilled into 950 feet- The 501111716 is CII1P05ed 0f 24%, y the formation while the Newtonian drive material is inllme, Water; Straight Tun g 111% of a jected into the formation at reduced rates. refined alkylnaphthenic monosulfonate purchased from The process f Claim 7 comprising reducing Shell Oil p y; and 33% iSopropahot- Wen P s'tantially to zero the rate at which the drive material is ing is 2.5 acres. Formation has a permeability of 150 injected into the f ti mi and a Porosity Of The initial on f 10. In a process for the production of petroleum fluids tion of the formation is t and Water Saturatlon from permeable subterranean formations having a pluis Gas and Voids. account for 18-27% of the 35 rality of wells drilled therein comprising injecting a vP vehlme- Crude viseoslty is about P- at pseudoplastic non-Newtonian fluid into said formation The oileexternalr,slg isfn l wcdhyne.figgpt uater: through a. portion of the wells drilled therein While e ter emulsion in an amount equlvalent to about 3% periodically reducing, and subsequently increasing, the 0f the P Volume, having a compositiqn (by Volume) rate at which the fluid is injected into the formation of 60.0% water; 32.2% straight run gasoline; 5.8% alkyl- 40 through said portion of Wells and producing Oil through naphthenic monosulfonate; and 2.0% isopropanol. The a second portion of Said plurality of Wells @he9 Y. .W9e. HiliX an apparent Yisccstty of P 11. The process of claim 10 comprising maintaining mately that of crudein the formation, as measured by negative pressures on the remaining portion of Wells a Brookfield viscometer. After injection of the soluble drilled into said formation oil and emul sion is c p wginie h i- 12. The process of claim 10 comprising reducing subf te miectwn 1s stopped for two days- Dunne the stantially to Zero the rate at which the fluid is injected period, the center production well of the five-spot is coninto the formation tinuously drawn down. After draw down of pressure in 13 The process of claim 10 comprising reducing the formation surrounding the center well is substantially Stahtiahy to Zero the rate at Which the fluid is injected complete injection is resumed at the rate t about 300 into the formation while continuously producing oil from h-P- at a Wellhead Pressure 99 lfnor to the remaining portion of the wells drilled into said lnterruption of injection, maximum ln ectivity is only formation b 160 1 1 As frontal velocity is related o 14. In a process for the recovery of petroleum fluids P t mlected: the velocltY the Pentneter of from permeable subterranean petroleum-bearing formamjficted fluld toward the S Well 15 Increased tions wherein a pseudoplastic non Newtonian fluid is intherefere, Y Y Tate e jected into the said formation through a plurality of W lls NOW havmg descnbed our mventlont What we damn areally external to a production well, the steps compris- In a ProcesS for the recovery f Petmteum fiulds ing periodically reducing, and subsequently increasing, from Permeable Subterranean formatlon hav mg at the rate at which the fluid is injected into the external one injection well and one production well drilled therein 0 Wells through the plurality of Wells areally external to Wherem a fluld havmg pseudoplastlc q the said production well and recovering oil through said characteristics in the reservoir is injected into the said production Welh formation through at least one injection well, the said 15 In a process for the recovery of petroleum fluids fluid is propelled through the said formation by t e fill from permeable subterranean petroleum-bearing formathel injection of fluid, and tormatlon flulds P e tions wherein a pseudoplastic non-Newtonian fluid is in .th1T l .gh a l 1.SI..9I r R QQ J i9 L & t the Steps QfhP jected into a row of injection wells drilled into said ..ih. l?.er k ttel l 939 at ttik gt wne petroleum-bearing formation and petroleum fluids are the fihld eXhlhltlng pseudoPlastle noh'Newtoman char recovered through an adjacent row of Wells drilled into acteristics, decreasing injection pressures and, after pres- Said petroleumhearing formation, the steps comprising Shire hflfillidli inereasing the t l t ptessutesperiodically reducing, and subsequently increasing the h Pt 0t elalm 1 etfmpnsmg continuously rate at which the fluid is injected into the formation p 011 through e P Yvetl(s)- through said row of injection wells and recovering oil 3. The process of claim 1 comprising reducing m ecthrough Said Production Welh tion pressures to substantially zero, while fluid recovery is continued at the production well(s). (References on following page) References Cited by the Examiner UNITED OTHER REFERENCES STATES PATENTS ff 166 4O XV, NO- 8 (TN 860 16) (pp. 877-884).

Beeson 166-9 5 CHARLES E. OCONNELL, Primary Examiner. Roper et a1. 1669 Turbak 166 9 X J. L. NACKENOFF, Examiner.

Meadors 166-9 S. J. NOVOSAD, Assistant Examiner.

Journal of Petroleum Technology, August 1963, vol. 

10. IN A PROCESS FOR THE PRODUCTION OF PETROLEUM FLUIDS FROM PERMEABLE SUBTERRANEAN FORMATIONS HAVING A PLURALITY OF WELLS DRILLED THEREIN COMPRISING INJECTING A PSEUDOPLASTIC NON-NEWTONIAN FLUID INTO SAID FORMATION THROUGH A PORTION OF THE WELLS DRILLED THEREIN WHILE 